1. Field of the Invention
Aspects of the present invention relate to an organic light emitting display device, and more particularly, to an organic light emitting display device that can reach the optimum light emitting efficiency of each pixel.
2. Description of the Related Art
Recently, portable thin flat display devices have been replacing standard display devices. Among flat display devices, organic light emitting display devices have the advantages of a large viewing angle, excellent contrast, and a quick response speed, and thus are being developed for the next generation of display devices.
Various attempts have been made to decrease power consumption and increase the efficiency of such organic light emitting display devices. For example, a material having a charged carrier with high mobility is used in a hole injection layer, a hole transport layer, or the like, so as to obtain low power consumption, high efficiency, and long durability.
However, when a full color device is manufactured using such a material having a charged carrier with high mobility, a horizontal leakage current may be generated because of the high mobility of the charged carrier in the hole injection layer and the hole transport layer. This is because the hole injection layer and the hole transport layer are formed from a common layer that is in turn formed over all pixels, and when one color is lighted, an adjacent pixel having a different color also lights up because of a horizontal leakage current. Accordingly, it is difficult to realize colors and to express gray scale in low luminescence.
Meanwhile, in a full color organic light emitting display device, pixels according to each color emit lights in different locations in a light emitting layer. For example, red and blue are emitted near the hole transport layer, and green is emitted near the electron transport layer. Here, the hole injection layer and the hole transport layer are formed of a material having a charged carrier with a high mobility, and when the hole injection layer and the hole transport layer are formed in the same location independent of the characteristics of each pixel, hole injection into the light emitting layer increases in each pixel. Accordingly, light emitting areas for red and blue exist within the light emitting layer, while the light emitting area for green is not in the light emitting layer but exists at the boundary of the light emitting area and the electron transport layer. Thus, the light emitting efficiency of red and blue may increase, while the light emitting efficiency of green may decrease.